This research project is concerned with a study of proteins which possess combining sites directed against carbohydrates. Of primary focus at this time is the isolation, purification and characterization of a class of carbohydrate-binding proteins from plant seeds known as lectins or phytohemagglutinins. These important proteins are being studied for a variety of reasons: they are models for antibodies, probes for investigating the distribution and structure of complex carbohydrates (glycoproteins and glycolipids) present at cell surfaces and as reagents for distinguishing between certain types of normal and neoplastic animal cells. Effort is being directed toward the physical and chemical characterization of lectins, ascertaining their carbohydrate-binding specificity and quantitating their binding for erythrocytes and lymphocytes. Also under investigation is the isolation of new lectins which have specificity for alpha-D-galactosyl units and which may be utilized as serological reagents for typing blood.